From: ebiederm@xmission.com (Eric W. Biederman)
To: Serge Hallyn <serge.hallyn@ubuntu.com>
Cc: Seth Forshee <seth.forshee@canonical.com>,
Jens Axboe <axboe@kernel.dk>,
Serge Hallyn <serge.hallyn@canonical.com>,
Arnd Bergmann <arnd@arndb.de>,
linux-kernel@vger.kernel.org,
LXC development mailing-list
<lxc-devel@lists.linuxcontainers.org>,
James Bottomley <James.Bottomley@HansenPartnership.com>,
Greg Kroah-Hartman <gregkh@linuxfoundation.org>
Subject: Re: [lxc-devel] [RFC PATCH 00/11] Add support for devtmpfs in user namespaces
Date: Fri, 23 May 2014 15:23:50 -0700 [thread overview]
Message-ID: <87ioow9ls9.fsf@x220.int.ebiederm.org> (raw)
In-Reply-To: <20140521223319.GF29211@ubuntumail> (Serge Hallyn's message of "Wed, 21 May 2014 22:33:19 +0000")
Serge Hallyn <serge.hallyn@ubuntu.com> writes:
> Quoting Eric W. Biederman (ebiederm@xmission.com):
>>
>>
>> >> Ultimately the technical challenge is how do we create a block device
>> >> that is safe for a user who does not have any capabilities to use, and
>> >> what can we do with that block device to make it useful.
>> >
>> > Yes, and I'd like to get started solving those challenges. But I also
>> > don't think we can address these two points (support partition blkdevs,
>> > help prevent more priveleged users from using a namespace's loop
>> > devices) sufficiently while having an implementation completely
>> > contained within the loop driver as Greg is requesting.
>>
>> My key take away from the conversation is that we should reduce the
>> scope of what is being done to something that makes sense and the
>> propblems are immediately visible.
>>
>> Part of me would like to suggest that fuse and it's ability to imitate
>> device nodes might be a more appropriate solution, to something that
>
> Do you have a link to more info on this? Some googling got me to an
> interesting but old thread on CUSE, but nothing specifically about fuse
> doing this.
CUSE is probably what I was thinking of. It is all part of the fuse
code base in the kernel. And now that I am reminded it is called CUSE
I go Duh that is a character device...
Fuse and everything it can do is definitely the filesystem I would like
to see most have the audits to be enabled in user namespace. Fuse
was built to be sufficiently paranoid to allow this and so it should not
take a lot to take fuse the rest of the way.
>> just needs block device access and nothing else.
>>
>> For purposes of discussion let's call it unprivloopfs. That can reuse
>> code from the loop device or not as appropriate. Not supporting
>> paritioning I think is a very reasonable first step until it is shown
>> that we can make good use of partitioning support, and there are not
>> better ways of solving the problem.
>>
>> I expect the most productive thing to talk about is what is your
>> immediate goal? Mounting a filesystem? Building an iso?
>
> For me it would be taking an iso and making some changes to it to
> localize it (i.e. take an install iso and add preseed file).
>
> Now of course in the end there is no reason why we can't do all of
> this with a new suite of libraries which simply uses read/write with
> knowledge of the fs layouts to parse and modify the backing files.
> My concern there is that duplicating all of the fs code seems unlikely
> to improve the soundness of either implementation. Perhaps we can
> autogenerate this from the kernel source? Does fuse already do
> something like that?
I am not aware of that. But I have not worked extensively with fuse.
I do agree that finding a way to perform a read-only mount of an ISO by
an unprivielged user is a very interesting use case. Given it's
interchange medium nature isofs should be as hardened as human possible,
and that is likely easier with a read-only filesystem. And at less than
4000 lines of code isofs is auditable.
So as a target for unprivileged mounts of a block device isofs looks
like a good place to start.
Eric
next prev parent reply other threads:[~2014-05-23 22:24 UTC|newest]
Thread overview: 76+ messages / expand[flat|nested] mbox.gz Atom feed top
2014-05-14 21:34 [RFC PATCH 00/11] Add support for devtmpfs in user namespaces Seth Forshee
2014-05-14 21:34 ` [RFC PATCH 01/11] driver core: Assign owning user namespace to devices Seth Forshee
2014-05-14 21:34 ` [RFC PATCH 02/11] driver core: Add device_create_global() Seth Forshee
2014-05-14 21:34 ` [RFC PATCH 03/11] tmpfs: Add sub-filesystem data pointer to shmem_sb_info Seth Forshee
2014-05-14 21:34 ` [RFC PATCH 04/11] ramfs: Add sub-filesystem data pointer to ram_fs_info Seth Forshee
2014-05-14 21:34 ` [RFC PATCH 05/11] devtmpfs: Add support for mounting in user namespaces Seth Forshee
2014-05-14 21:34 ` [RFC PATCH 06/11] drivers/char/mem.c: Make null/zero/full/random/urandom available to " Seth Forshee
2014-05-14 21:34 ` [RFC PATCH 07/11] block: Make partitions inherit namespace from whole disk device Seth Forshee
2014-05-14 21:34 ` [RFC PATCH 08/11] block: Allow blkdev ioctls within user namespaces Seth Forshee
2014-05-14 21:34 ` [RFC PATCH 09/11] misc: Make loop-control available to all " Seth Forshee
2014-05-14 21:34 ` [RFC PATCH 10/11] loop: Assign devices to current_user_ns() Seth Forshee
2014-05-14 21:34 ` [RFC PATCH 11/11] loop: Allow priveleged operations for root in the namespace which owns a device Seth Forshee
2014-05-23 5:48 ` Marian Marinov
2014-05-26 9:16 ` Seth Forshee
2014-05-26 15:32 ` [lxc-devel] " Michael H. Warfield
2014-05-26 15:45 ` Seth Forshee
2014-05-27 1:36 ` Serge E. Hallyn
2014-05-27 2:39 ` Michael H. Warfield
2014-05-27 7:16 ` Seth Forshee
2014-05-27 13:16 ` Serge Hallyn
2014-05-15 1:32 ` [RFC PATCH 00/11] Add support for devtmpfs in user namespaces Greg Kroah-Hartman
2014-05-15 2:17 ` [lxc-devel] " Michael H. Warfield
2014-05-15 3:15 ` Seth Forshee
2014-05-15 4:00 ` Greg Kroah-Hartman
2014-05-15 13:42 ` Michael H. Warfield
2014-05-15 14:08 ` Greg Kroah-Hartman
2014-05-15 17:42 ` Serge Hallyn
2014-05-15 18:12 ` Seth Forshee
2014-05-15 22:15 ` Greg Kroah-Hartman
2014-05-16 1:42 ` Michael H. Warfield
2014-05-16 7:56 ` Richard Weinberger
2014-05-16 19:20 ` James Bottomley
2014-05-16 19:42 ` Michael H. Warfield
2014-05-16 19:52 ` [lxc-devel] Mount and other notifiers, was: " James Bottomley
2014-05-16 20:04 ` Michael H. Warfield
2014-05-16 1:49 ` [lxc-devel] " Serge Hallyn
2014-05-16 4:35 ` Greg Kroah-Hartman
2014-05-16 14:06 ` Seth Forshee
2014-05-16 15:28 ` Michael H. Warfield
2014-05-16 15:43 ` Seth Forshee
2014-05-16 18:57 ` Greg Kroah-Hartman
2014-05-16 19:28 ` James Bottomley
2014-05-16 20:18 ` Seth Forshee
2014-05-20 0:04 ` Eric W. Biederman
2014-05-20 1:14 ` Michael H. Warfield
2014-05-20 14:18 ` Serge Hallyn
2014-05-20 14:21 ` Seth Forshee
2014-05-21 22:00 ` Eric W. Biederman
2014-05-21 22:33 ` Serge Hallyn
2014-05-23 22:23 ` Eric W. Biederman [this message]
2014-05-28 9:26 ` Seth Forshee
2014-05-28 13:12 ` Serge E. Hallyn
2014-05-28 20:33 ` Eric W. Biederman
2014-05-18 2:42 ` Serge E. Hallyn
2014-05-17 4:31 ` Eric W. Biederman
2014-05-17 16:01 ` Seth Forshee
2014-05-18 2:44 ` Serge E. Hallyn
2014-05-19 13:27 ` Seth Forshee
2014-05-20 14:15 ` Serge Hallyn
2014-05-20 14:26 ` Serge Hallyn
2014-05-17 12:57 ` Michael H. Warfield
2014-05-15 18:25 ` Richard Weinberger
2014-05-15 19:50 ` Serge Hallyn
2014-05-15 20:13 ` Richard Weinberger
2014-05-15 20:26 ` Serge E. Hallyn
2014-05-15 20:33 ` Richard Weinberger
2014-05-19 20:22 ` Andy Lutomirski
2014-05-20 14:19 ` Serge Hallyn
2014-05-23 8:20 ` Marian Marinov
2014-05-23 13:16 ` James Bottomley
2014-05-23 16:39 ` Andy Lutomirski
2014-05-24 22:25 ` Serge Hallyn
2014-05-25 8:12 ` James Bottomley
2014-05-25 22:24 ` Serge E. Hallyn
2014-05-28 7:02 ` James Bottomley
2014-05-28 13:49 ` Serge Hallyn
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